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Grade 10 Science: Conservation of Energy Lab Name:___________________ Partner:__________________ Materials: Metersticks, String, Stopwatch, Ring Stand, Masses, Protractor Objectives: 1. Provide experimental and graphical evidence that the bob mass and release angle do not affect the period of a pendulum. 2. Using experimental data determine a graphical relationship between the period of a pendulum and its length. Concepts: The period of a pendulum is the time required for its bob to complete one oscillation. The period of a pendulum is affected only by its length and the force provided by gravity and is expressed by the equation: Procedure I: Changing Mass 1. Use items from the materials list to set up a pendulum. Record your pendulum’s string length and mass of the bob. 2. Using a protractor select and record a release angle for your pendulum. This angle should not be greater than 25 3. Release the pendulum and record the time it takes the bob to complete 3 full oscillations. Divide this number by three and record the period of the pendulum. 4. Keeping a constant release angle repeat step 3 an additional three times. Record the average of these four trials to obtain an accurate value for the period of the pendulum. 5. Keeping every other variable constant, repeat steps 3 and 4 an additional three more times but change the mass of the bob each time. Record this information. This should provide you with a total of four mass trials. Procedure II: Changing Release angle 6. Using your original bob mass, repeat steps 2, 3 and 4; however, change the release angle of the pendulum. 7. Keeping every other variable constant, repeat step 6 an additional two more times but change the release angle of the bob each time. Record this information. This should provide you with a total of four angle trials (your original from steps 2 and 3, your new angle from step 6 and the additional 2 angles from step 7). Procedure III: Changing string length 8. Using your original bob mass and release angle, repeat steps 2, 3 and 4; however, change the pendulum string length. 9. Keeping every other variable constant, repeat step 8 an additional two more times but change the length of the pendulum each time. Record this information. This should provide you with a total of four length trials (your original from steps 2 and 3, your new length from step 8 and the additional 2 lengths from step 9). Data Processing: For each procedure construct a data table that displays the raw AND processed data for each of the 4 trials (and 4 sub-trials) performed. These tables should be neat, organized, contain units and a brief title. Do not forget to record the data for the constant variables as well. Construct a graph for each of the three procedures. Your independent variable should go on the x- axis while your dependent variable (period) should go on the y-axis. Do not forget your line of best fit! Note: ALL of your raw AND processed data should be presented in tables that are neat, organized, understandable and fully labeled. A person that has no prior knowledge of this lab should be able to read these tables and understand the experiment. You must show one example (a fully worked out example) of every type of calculation performed. All graphs must be neat, organized, understandable and fully labeled. Questions: 1. Using your third graph predict how long you would have to make a rope swing if you wanted the swing’s period to be 5 seconds? Would this period differ if you or your smaller brother was swinging on the rope? Explain. 2. If you set up your pendulum atop Mt. Everest, would the period be less than, the same as, or greater than it would be in your lab? Explain. 3. How would the shape of your third graph change if you were to plot the pendulum’s frequency instead of its period on the y-axis. Sketch a rough drawing of the basic shape of this graph (you do not need graph paper). 4. Using the equation for the period of a pendulum, calculate out the 4 predicted periods for your procedure III pendulum string lengths. Using these values and your actual experimental period values, determine the overall percent error for procedure III. Explain what might have caused this error.
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